The present invention relates to transparent long wave infrared absorbing systems, and in particular to such systems employing a flexible plastic substrate.
To efficiently utilize solar energy, it is often desirable to collect solar energy within a spatial volume, and trap the solar energy within said volume. Solar energy is concentrated primarily in wavelengths ranging from 0.4 to 2.5 microns, including the visible spectrum from 0.4 to 0.7 microns and the near infrared spectrum from 0.7 to 2.5 microns. When such solar energy strikes an object, it is generally reradiated as heat energy, which is concentrated in the long wave infrared spectrum from approximately 2.5 to 50 microns. Accordingly, to efficiently trap solar energy within a spatial volume, it is essential to allow radiation within the solar spectrum to pass into the volume, but prevent radiation in the long wave infrared region from escaping therefrom.
A variety of different types of compounds have been developed which are generally transmissive to radiation in the solar spectrum but opaque to radiation in a long wave infrared radiation spectrum. However, all such materials generally require that they be applied to a glass or thick inflexible acrylic substrate. Such compounds now in use typically require high heat or solvents in their application process and cannot be applied to thin, flexible plastic. As a result, such materials are quite expensive, difficult to work with and very difficult to retrofit in existing structures.